Book Image

GNU/Linux Rapid Embedded Programming

By : Rodolfo Giometti
Book Image

GNU/Linux Rapid Embedded Programming

By: Rodolfo Giometti

Overview of this book

Embedded computers have become very complex in the last few years and developers need to easily manage them by focusing on how to solve a problem without wasting time in finding supported peripherals or learning how to manage them. The main challenge with experienced embedded programmers and engineers is really how long it takes to turn an idea into reality, and we show you exactly how to do it. This book shows how to interact with external environments through specific peripherals used in the industry. We will use the latest Linux kernel release 4.4.x and Debian/Ubuntu distributions (with embedded distributions like OpenWrt and Yocto). The book will present popular boards in the industry that are user-friendly to base the rest of the projects on - BeagleBone Black, SAMA5D3 Xplained, Wandboard and system-on-chip manufacturers. Readers will be able to take their first steps in programming the embedded platforms, using C, Bash, and Python/PHP languages in order to get access to the external peripherals. More about using and programming device driver and accessing the peripherals will be covered to lay a strong foundation. The readers will learn how to read/write data from/to the external environment by using both C programs or a scripting language (Bash/PHP/Python) and how to configure a device driver for a specific hardware. After finishing this book, the readers will be able to gain a good knowledge level and understanding of writing, configuring, and managing drivers, controlling and monitoring applications with the help of efficient/quick programming and will be able to apply these skills into real-world projects.
Table of Contents (26 chapters)
GNU/Linux Rapid Embedded Programming
Credits
About the Author
About the Reviewer
www.PacktPub.com
Customer Feedback
Preface

What is a GPIO line?


A General Purposes Input Output (GPIO) line is a pin of a microcontroller or CPU or other integrated circuit whose behavior is controllable by the user at runtime. So, a GPIO pin has no predefined usage, but the developer has the ability to set it for input or output usage (for simpler implementations) or as an IRQ source or other functionalities.

In general, a GPIO line can:

  • Be enabled/disabled.

  • Be configured as input or output.

  • Have readable/writable output values (typically, high is 1 and low is 0).

  • Have readable input values (typically, high is 1 and low is 0).

  • Have default pulled-up or pulled-down input values.

  • Have input values to be used as IRQ source.

The GPIO lines are so generic that if adequately used in a dedicated program, they can be used to emulate another digital interface controller; in fact, inside the Linux kernel, we can find several kinds of peripheral controllers emulated via GPIO (the most famous and used are the keyboard, I2C and W1 controllers; in particular...